Separate the chicken legs into thighs and drumsticks; cut each breast in half diagonally through the bone. In a medium plastic container with a lid or a medium bowl, stir together the buttermilk, salt, and pepper. Add the chicken, turning to coat well. Place the lid on the container or cover the bowl with plastic wrap and refrigerate for at least two hours or up to, but not exceeding, twelve hours.
In another container, whisk together the flour, baking powder, thyme, garlic powder, paprika, salt, and pepper. Drizzle in the buttermilk and stir to form small crumbs. Remove the chicken pieces from the buttermilk mixture and coat well in the flour mixture. Place the coated chicken on a rack to rest for 20-30 minutes at room temperature.
Place a deep, heavy skillet or pot with a lid, preferably cast iron, over medium-high heat and add the vegetable shortening. The shortening should measure 1/2-inch in the skillet. Heat the shortening to 350ºF on a candy/oil thermometer. Gently lay a few chicken pieces skin side down in the hot fat and cover. Cook for 10 minutes, checking after 5 minutes and moving the pieces if they are browning unevenly or too quickly. (At this point the fat should be bubbling and register between 250ºF and 300ºF on the thermometer.) Remove the lid and turn the chicken with tongs and cook, uncovered, until the second side is richly browned, about 10-12 minutes. Remove the chicken to a rack set over a baking sheet to drain. Chicken can be kept warm in an oven set at the lowest setting or it can be safely held at room temperature for several hours loosely covered with wax paper. Leftovers must be refrigerated. Enjoy!